Rapid progression of methotrexate-associated lymphoproliferative disorder presenting with multiple pulmonary masses in rheumatoid arthritis patient: A case report.

Lymphoproliferative disorders (LPDs) are relatively rare but serious complications in patients with rheumatoid arthritis undergoing immunosuppressive therapy. Here, we report a case of methotrexate-associated LPD (MTX-LPD) in a 74-year-old patient with rheumatoid arthritis who presented with multiple pulmonary nodules. Lung biopsy confirmed Epstein-Barr virus-positive diffuse large B-cell lymphoma. The patient had been on low-dose MTX for over 17 years. Notably, lymphocyte counts were persistently low before LPD onset and gradually improved following MTX discontinuation. Despite the spontaneous regression of LPD following MTX withdrawal and steroid therapy, a second exacerbation occurred, necessitating additional treatment. Fluctuations in lymphocyte count and C-reactive protein levels demonstrated an inverse correlation throughout the disease course. This suggests a strong association between immune reconstitution and LPD remission. We hypothesised that immunosenescence, including age-related changes in T and B-cells, may contribute to impaired immune surveillance and delayed disease resolution. Monitoring lymphocyte counts may be a useful marker for early detection and prognosis of MTX-LPD.